An airtight house might benefit your heating bill, but it can wreak havoc on your health.

By Nancy Kalish

Exhaust fumes, smog, secondhand smoke: When you step outside, you expect to be exposed to unhealthy elements lurking in the air. But if you think staying indoors is automatically safer, think again. Your home can be up to five times more polluted with common organic chemicals than outdoor air, according to the Environmental Protection Agency (EPA). And in winter, as you keep windows locked tight to seal in warmth, you could be inhaling a concentrated cocktail of potentially dangerous chemicals found in products like air fresheners and cleaning supplies.